Koji Mold Growing

Learn the science behind mycelia and the fermentation of mold grown directly on the surface of the meat called Koji Charcuterie.

| April 2019

Photo Courtesy of New Society Publishers

Koji Charcuterie  

Koji charcuterie is a method of preserving meat that relies on Aspergillus oryzae, or koji mold, grown directly on the surface of the meat. This mold is a filamental fungus (as is P. nalgiovense), which might seem weird, since most people think of fungus as a typical Mario Brothers mushroom. The truth is that fungi come in many shapes, sizes and colors, and the "mushroom" you picture is just  the fruiting body of the dynamic fungus - its way of  getting  its "seed" out to the world. If you think about it, this isn’t too crazy. The familiar apple, for example, is really just an ovary, holding the  seed  of  the  apple tree. Likewise, there is more to fungus than its fruiting body. What more? Well, the mycelium, which you can think of as the fungus's "roots." Mycelia are  highly  networked,  forming  mats  and  webs, and are responsible for incredibly dynamic metabolic activity in the life of any fungus. Understanding this may help you recognize surface molds such as penicillium and koji as fungi indeed. In warm, moist environments rich in oxygen, koji can grow on the surface of nearly anything, and what you'll see is a literal mat of filamental white, yellow or pale-green mycelia, growing all  over the substrate. I've heard of koji mold being used to break down plastic (seriously), and using the same metabolism, it can work its magic on meat as well.

The science of how koji works is a bit more complex than we have room to explore, but the main thing to understand is that its mycelial mat produces many enzymes, which work to break big molecules into smaller ones. The bigger molecules we're talking about here are starches, carbohydrates, proteins and fats, and they are being reduced to simpler sugars, amino acids, fatty acid chains, etc. With what you know about fermentation and curing so far, you might be able to guess that these smaller molecules are prime nutrition for some other microorganisms (like our friend Lactobacillus), and in this way, koji lays a spectacular groundwork for natural fermentation processes to unfold. But, in tandem with other microbes, koji’s enzymes have their own added effects. For example, it has been found that typically tough cuts of meat can be cultured with koji spores; once the koji populates their surface and releases its enzymes into the meat, it radically tenderizes the cuts. Additionally, meat that is cured using koji has been shown to cure in at least a third of the time that meat cures using traditional charcuterie  practice, due to the ongoing activity of koji's enzymes during the curing process . It 's truly amazing.

I'm not an expert on koji charcuterie, and have only recently been introduced to the power of koji across all of its applications, from miso to soy sauce to sake and vinegars. I'm extremely excited about the applications, however, and am now happily growing koji like a fiend, right next to my desk. I grow it on everything from rice to bar­ley to pork loins, after the advice of Chef Jeremy Umansky, the leader in koji charcuterie, using methods he developed at his restaurant in Ohio. Chef Umansky has contributed his own recipe to this chapter, so you ca n get a sense of how the experts are working with koji and meat. I've also included my own koji experiment, a recipe I am developing for a local restaurant here in Asheville, NC. Umansky is working on his own books and is totally open sourcing his projects online. Do yourself a favor and check out his restaurant, Larder, and the social media associated with the exciting work he is doing.

Growing Koji

Like any mold, koji prefers warmth and moisture. Temperatures of roughly 80-95 degrees Fahrenheit and high humidity levels are ideal for koji to thrive. Since this is decidedly not the ideal environment for your home, you'll have to rig up a small incubator for your koji projects. My incubator is made from a 12-x-24-inch plastic tub about 6 inches deep, with a lid. I fill it about a third of the way with water, and in that water, I place a roughly $40 aquarium heater, capable of heating water up to 90 degrees. You can find these anywhere they sell tropical fish. The aquarium thermometer is plugged into the wall beside my desk, and then run into the water and suctioned to the bottom of the plastic bin. I crank it all the way up to 88 degrees, then invert a couple of small loaf pans in the water, allowing me to place a 9-x-13-inch glass casserole pan on top of them so that the casserole pan is submerged in the water but not loosely floating. Then whatever I am koji culturing can hang out in the casserole pan, covered in a towel, and happily form sweetly fragrant koji mold on its surf ace. I typically cover whatever I am culturing in a tea towel, which I change out daily. This prevents any condensation from drip­ ping consistently on the food. While koji likes high humidity, I find that it helps to keep whatever you are culturing from getting down right soaked.

So, how do you get the koji on there to begin with? The answer is, you'll need to buy a starter culture. I know I kind of scoffed at this earlier, but it is important to understand that koji is relatively difficult to conjure from the wild. Research into ancient Asian  methods for doing this show they involve making strange cake-like concoctions from as many as twenty different native wild plants, and allowing these to ferment wrapped in leaves until the mycelial mat forms on their surface. Assuming you don't have the flora of a Chinese mountainside at your disposal, it is best to start by buying koji spores from reputable independent sources. My favorite provider is GEM Cultures. There are several types of koji, and they are grown on different grains. My favorite is barley koji, but you can choose what you want. Once you've picked it out, it will be mailed to you in a little bag with instructions for use. It looks like olive green powder.



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